There are several functions in migration related code that we need to evaluate if we can use kStrictlyNotIdempotent instead of kNoRetry.

Since RetryableError is always safe to retry, it should in theory be possible.

• MigrationBatchFetcher::_fetchBatch (migration_batch_fetcher.cpp)
• 2 instances in MigrationDestinationManager::_migrateDriver (migration_destination_manager.cpp)
• getNextSessionOplogBatch (session_catalog_migration_destination.cpp)